Photodynamic therapy mediates the oxygen-independent activation of hypoxia-inducible factor 1alpha

An oxygen-generating metal organic framework nanoplatform as a “synergy motor” for extricating dilemma over photodynamic therapy

Photodynamic therapy (PDT) combined with metal organic frameworks (MOFs) addresses current obstacles.

Combined Photodynamic and Photothermal Therapy and Immunotherapy for Cancer Treatment: A Review

Photoactivation therapy based on photodynamic therapy (PDT) and photothermal therapy (PTT) has been identified as a tumour ablation modality for numerous cancer indications, with photosensitisers and photothermal conversion agents playing important roles in the phototherapy process, especially in recent decades. In addition, the iteration of nanotechnology has strongly promoted the development of phototherapy in tumour treatment. PDT can increase the sensitivity of tumour cells to PTT by interfering with the tumour microenvironment, whereas the heat generated by PTT can increase blood flow, improve oxygen supply and enhance the PDT therapeutic effect. In addition, tumour cell debris generated by phototherapy can serve as tumour-associated antigens, evoking antitumor immune responses. In this review, the research progress of phototherapy, and its research effects in combination with immunotherapy on the treatment of tumours are mainly outlined, and issues that may need continued attention in the future are raised.

Inhibition of hypoxia-inducible factor 1 by acriflavine renders glioblastoma sensitive for photodynamic therapy

BACKGROUND

photodynamics therapy (PDT) induces tumor cell death through oxidative stress and is closely associated with the expression of hypoxia inducible factor-1a (HIF1a), which activates multiple downstream survival signaling pathways. Therefore, the purpose of this study was to investigate the expression levels of HIF1a proteins in PDT-treated GBM cells and to determine whether inhibition of HIF1a reduces survival signals to enhance the efficacy of PDT.

RESULTS

PDT combined with Acriflavine (ACF, PA) decreased the expression of HIF1a and regulated the downstream expression of GLUT-1, GLUT-3, HK2 and other gluconeogenic pathway proteins. PA group significantly suppressed tumor growth to improve the efficacy of PDT.

METHODS

We first performed the correlation of HIF1a, GLUT-1, GLUT-3, and HK2, and quantified the expression of HIF1a on tumor grades and IDH mutation classification by TCGA and CGGA databases. Then, we used immunohistochemistry method to detect four gene expression levels in human GBM tissues. Besides, we examined the effects of different treatments on the proliferation, migration and invasion ability of GBM cell lines by CCK8, wound healing and transwell assays. ACF, a HIF1a/HIF1β dimerization inhibitor, was used to evaluate its adjuvant effect on the efficacy of PDT.

CONCLUSION

HIF1a is activated in GBM cell lines and contributes to the survival of tumor cells after PDT in vitro and in vivo. PA group inhibited HIF1a expression and improved PDT efficacy in the treatment of recalcitrant GBM.

Study of copper-cysteamine based X-ray induced photodynamic therapy and its effects on cancer cell proliferation and migration in a clinical mimic setting

Copper-cysteamine as a new generation of sensitizers can be activated by light, X-rays, microwaves, or ultrasound to produce reactive oxygen species. X-ray induced photodynamic therapy (X-PDT) has been studied extensively; however, most of the studies reported so far were conducted in the laboratory, which is not conducive to the clinical translation conditions. In this contribution, for the first time, we investigated the treatment efficiency of copper-cysteamine (Cu-Cy) based X-PDT by mimicking the clinical conditions with a clinical linear accelerator and building deep-seated tumor models to study not only the effectiveness but also its effects on the cell migration and proliferation in the level of the cell, tissue, and animal. The results showed that, without X-ray irradiation, Cu-Cy nanoparticles (NPs) had a low toxicity in HepG2, SK-HEP-1, Li-7, and 4T1 cells at a concentration below 100 mg/L. Interestingly, for the first time, it was observed that Cu-Cy mediated X-PDT can inhibit the proliferation and migration of these cell lines in a dose-dependent manner. Antigen markers of migration and cell proliferation, proliferating cell nuclear antigen (PCNA) and E-cadherin, from tumor tissue in the X-PDT group were remarkably different from that of the control group. Furthermore, the MRI assessment showed that the Cu-Cy based X-PDT inhibited the growth of deeply located tumors in mice and rabbits (p < 0.05) without any obvious toxicities in vivo. Overall, these new findings demonstrate that Cu-Cy NPs have a safe and promising clinical application prospect in X-PDT to improve the efficiency of radiotherapy (RT) for deep-seated tumors and effectively inhibit tumor cell proliferation and migration.

Self-Remedied Nanomedicine for Surmounting the Achilles' Heel of Photodynamic Tumor Therapy

Oxygen-dependent photodynamic therapy (PDT) could exacerbate tumor hypoxia to induce the upregulation of hypoxia-inducible factor-1α (HIF-1α), which would promote tumor growth and metastasis. In this paper, a self-remedied nanomedicine is developed based on a photosensitizer and a HIF-1α inhibitor to surmount the Achilles' heel of PDT for enhanced antitumor efficacy. Specifically, the nanomedicine (designated as CYC-1) is prepared by the self-assembly of chlorine e6 (Ce6) and 3-(5'-hydroxy-methyl-2'-furyl)-1-benzylindazole (YC-1) through π-π stacking and hydrophobic interactions. Of special note, carrier-free CYC-1 holds an extremely high drug loading rate and avoids excipient-triggered adverse reactions. Intravenously administered CYC-1 prefers to accumulate in the tumor tissue for effective cellular uptake. More importantly, it is verified that CYC-1 is capable of inhibiting the HIF-1α activity, thereby improving its PDT efficacy on tumor suppression. Besides, CYC-1 has the overwhelming superiority in restraining tumor proliferation over the combined administration of Ce6 and YC-1, which highlights the advantage of this self-remedied strategy in drug delivery and tumor therapy. This study sheds light on the development of self-delivery nanomedicine for efficient PDT against malignancies.

Mechanistic insights into ceramidase inhibitor LCL521-enhanced tumor cell killing by photodynamic and thermal ablation therapies

Our recent investigation uncovered that the acid ceramidase inhibitor LCL521 enhances the direct tumor cell killing effect of photodynamic therapy (PDT) treatment. The present study aimed at elucidating the mechanisms underlying this effect. Exposing mouse squamous cell carcinoma SCCVII cells treated with temoporfin-based PDT to LCL521 (rising ceramide concentration) produced a much greater decrease in cell survival than comparable exposure to the sphingosine kinase-1 inhibitor PF543 (that reduces sphingosine-1-phosphate concentration). This is consistent with recognizing the rising levels of pro-apoptotic sphingolipid ceramide as being more critical in promoting the death of PDT-treated cells than the reduction in the availability of pro-survival acting sphingosine-1 phosphate. This pro-apoptotic impact of LCL521, which was suppressed by the apoptosis inhibitor bongkrekic acid, involves the interaction with the cellular stress signaling network. Hence, inhibiting the key elements of these pathways markedly influenced the adjuvant effect of LCL521 on the PDT response. Particularly effective was the inositol-requiring element-1 (IRE1) kinase inhibitor STF-083010 that dramatically enhanced the killing of cells treated with PDT plus LCL521. An important role in the survival of these cells was exhibited by master transcription factors STAT3 and HIF-1α. The STAT3 inhibitor NSC 74859 was especially effective in further reducing the cell survival rates, suggesting its possible exploitation for therapeutic gain. An additional finding in this study is that LCL521-promoted PDT-mediated cell killing through ceramide-mediated lethal effects is extended to the interaction with other cancer treatment modalities with a rapid cellular stress impact such as photothermal therapy (PTT) and cryoablation therapy (CAT).

Tailoring photosensitive ROS for advanced photodynamic therapy

Photodynamic therapy (PDT) has been considered a noninvasive and cost-effective modality for tumor treatment. However, the complexity of tumor microenvironments poses challenges to the implementation of traditional PDT. Here, we review recent advances in PDT to resolve the current problems. Major breakthroughs in PDTs are enabling significant progress in molecular medicine and are interconnected with innovative strategies based on smart bio/nanomaterials or therapeutic insights. We focus on newly developed PDT strategies designed by tailoring photosensitive reactive oxygen species generation, which include the use of proteinaceous photosensitizers, self-illumination, or oxygen-independent approaches. While these updated PDT platforms are expected to enable major advances in cancer treatment, addressing future challenges related to biosafety and target specificity is discussed throughout as a necessary goal to expand the usefulness of PDT.

Comparison of actual and simulated tumoricidal effects induced by photodynamic therapy

OBJECTIVES

Numerous studies employ mathematical methods, such as Monte Carlo simulation, to predict the tumor killing effects of photodynamic therapy (PDT) by simulating optical propagation, photosensitizer distribution, and oxygen distribution. Whether these models faithfully reflect tumor killing is unknown, and model validation using tumor cross sections in these studies is usually insufficient to answer this question. To fill this gap in our knowledge, we employed a mouse model of breast cancer to determine the spatiotemporal effects of PDT using direct histopathological and biochemical analyses of whole tumors.

METHODS

We prepared approximately 700 5-μm-thick serial sections of breast tumors of syngeneic mice treated with PDT employing the photosensitizer photocarcinorin (PsD-007, a second-generation photosensitizer developed in China). Three adjoining sections were subjected to hematoxylin and eosin staining to assess necrosis, the TUNEL assay to evaluate apoptosis, and CD31 staining to detect angiogenesis, respectively. We then generated a three-dimensional (3D) reconstruction of the tumor to evaluate these processes. We simultaneously used the Monte Carlo method to develop a model of light distribution throughout the tumor to evaluate the actual and simulated tumor killing effects induced by PDT.

RESULTS

Tumor necrosis decreased exponentially as a function of distance from the source of illumination, while the distributions of apoptosis and neovascularization were independent of light distribution. Most apoptosis occurred in the lower layers (3000-4000 μm) of the tumor where the light intensity was too low to excite the photosensitizer. Neovascularization occurred at depths ranging from 2500 to 3500 μm. These analyses provided a 3D view of how a tumor is destroyed using PDT.

CONCLUSIONS

Although the optical distribution model predicted tumor necrosis caused by PDT, it was ineffective in predicting the sites of apoptosis and vascular destruction. Mathematical modeling is limited in its capabilities required to gain a comprehensive understanding of the spatiotemporal events associated with PDT. The mouse model developed here will serve as a platform for detailed direct histopathological, biochemical, and molecular genetic analyses of the effects of PDT, which will facilitate the development of optimized treatment strategies.

Designing Stimuli-Responsive Upconversion Nanoparticles that Exploit the Tumor Microenvironment

Tailoring personalized cancer nanomedicines demands detailed understanding of the tumor microenvironment. In recent years, smart upconversion nanoparticles with the ability to exploit the unique characteristics of the tumor microenvironment for precise targeting have been designed. To activate upconversion nanoparticles, various bio-physicochemical characteristics of the tumor microenvironment, namely, acidic pH, redox reactants, and hypoxia, are exploited. Stimuli-responsive upconversion nanoparticles also utilize the excessive presence of adenosine triphosphate (ATP), riboflavin, and Zn²⁺ in tumors. An overview of the design of stimulus-responsive upconversion nanoparticles that precisely target and respond to tumors via targeting the tumor microenvironment and intracellular signals is provided. Detailed understanding of the tumor microenvironment and the personalized design of upconversion nanoparticles will result in more effective clinical translation.

Recapitulation of Hypoxic Tumor-stroma Microenvironment to Study Photodynamic Therapy Implications

Tumor microenvironment (TME) is a dynamic ecosystem where fibroblasts are recruited in order to provide a niche to support growth and, in some extent, to promote therapeutic resistance. However, the role of fibroblasts in stimulating or impairing photodynamic therapy (PDT) outcome has not yet been fully addressed. PDT is based on interactions between light, oxygen and photosensitizer, leading to phototoxic reactions that culminate in cell death. In this study, we demonstrated the consequences of a hypoxic stromal phenotype on tumor mass for exploring PDT response. We mimicked TME complexity implementing colon cancer cells and fibroblasts 3D cultures called spheroids. Using hypoxia reporting lines, we verified that homotypic spheroids exhibited a size-dependent transcriptional HIF-1 activity. When cocultured, fibroblasts were localized in the hypoxic core. In homotypic stromal spheroids, the distribution of the endogenous photosensitizer PpIX was homogeneous while decreased in hypoxic areas of tumor 3D cultures. When monocultured, fibroblasts were more efficient to produce PpIX from its prodrug Me-ALA. Interestingly, the cross talk between cancer cells and fibroblasts attenuated PpIX accumulation and conferred tumor PDT resistance when compared to homotypic 3D cultures. Overall, our data suggest that stroma and tumor act in an integrated, reciprocal fashion which could ultimately influence on therapeutic response.

P-21-activated kinase 1 contributes to tumor angiogenesis upon photodynamic therapy via the HIF-1α/VEGF pathway

Photodynamic therapy (PDT) is an effective oncotherapy and has been approved for clinical application. Unfortunately, its therapeutic efficacy is usually overshadowed by tumor angiogenesis. Thus, a detailed understanding of the tumor angiogenesis upon PDT is imperative. This study aimed to investigate the potential contribution and mechanism of P-21-activated kinase 1 (PAK1) in PDT-induced tumor angiogenesis. Firstly, we found that PAK1 was upregulated upon PDT and associated with tumor angiogenesis. Then, we elucidated the underlying molecular mechanism. Activation of PAK1 prevents hypoxia-inducible factor 1 alpha (HIF-1α) protein from ubiquitin-mediated degradation. Thereafter, HIF-1α accumulation results in the upregulation of vascular endothelial growth factor (VEGF), thus promoting tumor angiogenesis. More importantly, we determined that PAK1 knockdown effectually repressed tumor angiogenesis, which contributes to enhance the therapeutic effect of PDT. Together, PAK1 is a potential novel pharmaceutical target for inhibiting PDT-induced tumor angiogenesis, and PAK1 suppression in combination with PDT may be a potentially effective strategy for anti-tumor therapy.

Molecular pathways in cancer response to photodynamic therapy

This minireview describes the complexity of the molecular mechanisms involved in the tumor response to photodynamic treatment (PDT). Different aspects of reactive oxygen (ROS) and nitrogen species (RNS) induced by PDT will be examined. In particular, we will discuss the effect of ROS and RNS on cell compartments and the main mechanisms of cell death induced by the treatment. Moreover, we will also examine host defense mechanisms as well as resistance to PDT.

A biomimetic cascade nanoreactor for tumor targeted starvation therapy-amplified chemotherapy

Targeted drug delivery with precisely controlled drug release and activation is highly demanding and challenging for tumor precision therapy. Herein, a biomimetic cascade nanoreactor (designated as Mem@GOx@ZIF-8@BDOX) is constructed for tumor targeted starvation therapy-amplified chemotherapy by assembling tumor cell membrane cloak and glucose oxidase (GOx) onto zeolitic imidazolate framework (ZIF-8) with the loading prodrug of hydrogen peroxide (H₂O₂)-sensitive BDOX. Biomimetic membrane camouflage affords superior immune evasion and homotypic binding capacities, which significantly enhance the tumor preferential accumulation and uptake for targeted drug delivery. Moreover, GOx-induced glycolysis would cut off glucose supply and metabolism pathways for tumor starvation therapy with the transformation of tumor microenvironments. Importantly, this artificial adjustment could trigger the site-specific BDOX release and activation for cascade amplified tumor chemotherapy regardless of the complexity and variability of tumor physiological environments. Both in vitro and in vivo investigations indicate that the biomimetic cascade nanoreactor could remarkably improve the therapeutic efficacy with minimized side effects through the synergistic starvation therapy and chemotherapy. This biomimetic cascade strategy would contribute to developing intelligent drug delivery systems for tumor precision therapy.

A preclinical model to investigate the role of surgically-induced inflammation in tumor responses to intraoperative photodynamic therapy

OBJECTIVE

Inflammation is a well-known consequence of surgery. Although surgical debulking of tumor is beneficial to patients, the onset of inflammation in injured tissue may impede the success of adjuvant therapies. One marker for postoperative inflammation is IL-6, which is released as a consequence of surgical injuries. IL-6 is predictive of response to many cancer therapies, and it is linked to various molecular and cellular resistance mechanisms. The purpose of this study was to establish a murine model by which therapeutic responses to photodynamic therapy (PDT) can be studied in the context of surgical inflammation.

MATERIALS AND METHODS

Murine models with AB12 mesothelioma tumors were treated with either surgical resection or sham surgery with tumor incision but no resection. The timing and extent of IL-6 release in the tumor and/or serum was measured using enzyme-linked immunosorbent assay (ELISA) and compared to that measured in the serum of 27 consecutive, prospectively enrolled patients with malignant pleural mesothelioma (MPM) who underwent macroscopic complete resection (MCR).

RESULTS

MPM patients showed a significant increase in IL-6 at the time MCR was completed. Similarly, IL-6 increased in the tumor and serum of mice treated with surgical resections. However, investigations that combine resection with another therapy make it necessary to grow tumors for resection to a larger volume than those that receive secondary therapy alone. As the larger size may alter tumor biology independent of the effects of surgical injury, we assessed the tumor incision model. In this model, tumor levels of IL-6 significantly increased after tumor incision.

CONCLUSION

The tumor incision model induces IL-6 release as is seen in the surgical setting, yet it avoids the limitations of surgical resection models. Potential mechanisms by which surgical induction of inflammation and IL-6 could alter the nature and efficacy of tumor response to PDT are reviewed. These include a wide spectrum of molecular and cellular mechanisms through which surgically-induced IL-6 could change the effectiveness of therapies that are combined with surgery. The tumor incision model can be employed for novel investigations of the effects of surgically-induced, acute inflammation on therapeutic response to PDT (or potentially other therapies). Lasers Surg. Med. 50:440-450, 2018. © 2018 Wiley Periodicals, Inc.

Transcriptional activation of HIF-1 by a ROS-ERK axis underlies the resistance to photodynamic therapy

Photodynamic therapy (PDT), a promising treatment option for cancer, involves the activation of a photosensitizer (PS) by local irradiation with visible light. Excitation of the PS leads to a series of photochemical reactions and consequently the local generation of harmful reactive oxygen species (ROS) causing limited or none systemic defects. However, the development of resistance to this promising therapy has slowed down its translation into the clinical practice. Thus, there is an increase need in understanding of the molecular mechanism underlying resistance to PDT. Here, we aimed to examine whether a relationship exists between PDT outcome and ROS-involvement in the resistance mechanism in photosensitized cancer cells. In order to recapitulate tumor architecture of the respective original tumor, we developed a multicellular three-dimensional spheroid system comprising a normoxic periphery, surrounding a hypoxic core. Using Me-ALA, a prodrug of the PS PpIX, in human colorectal spheroids we demonstrate that HIF-1 transcriptional activity was strongly up-regulated and mediates PDT resistant phenotype. RNAi knockdown of HIF-1 impairs resistance to PDT. Oxidative stress-mediated activation of ERK1/2 followed PDT was involved on positive modulation of HIF-1 transcriptional activity after photodynamic treatment. ROS scavenging and MEK/ERK pathway inhibition abrogated the PDT-mediated HIF-1 upregulation. Together our data demonstrate that resistance to PDT is in part mediated by the activation of a ROS-ERK1/2-HIF-1 axis, thus, identifying novel therapeutic targets that could be used in combination with PDT.

A novel HIF-1α/VMP1-autophagic pathway induces resistance to photodynamic therapy in colon cancer cells

This is the first report showing that PDT-induced autophagy is directly mediated by HIF-1α and linked to VMP1 as a PDT-induced resistance mechanism.

Inhibition of hypoxia inducible factor 1 and topoisomerase with acriflavine sensitizes perihilar cholangiocarcinomas to photodynamic therapy

BACKGROUND

Photodynamic therapy (PDT) induces tumor cell death by oxidative stress and hypoxia but also survival signaling through activation of hypoxia-inducible factor 1 (HIF-1). Since perihilar cholangiocarcinomas are relatively recalcitrant to PDT, the aims were to (1) determine the expression levels of HIF-1-associated proteins in human perihilar cholangiocarcinomas, (2) investigate the role of HIF-1 in PDT-treated human perihilar cholangiocarcinoma cells, and (3) determine whether HIF-1 inhibition reduces survival signaling and enhances PDT efficacy.

RESULTS

Increased expression of VEGF, CD105, CD31/Ki-67, and GLUT-1 was confirmed in human perihilar cholangiocarcinomas. PDT with liposome-delivered zinc phthalocyanine caused HIF-1α stabilization in SK-ChA-1 cells and increased transcription of HIF-1α downstream genes. Acriflavine was taken up by SK-ChA-1 cells and translocated to the nucleus under hypoxic conditions. Importantly, pretreatment of SK-ChA-1 cells with acriflavine enhanced PDT efficacy via inhibition of HIF-1 and topoisomerases I and II.

METHODS

The expression of VEGF, CD105, CD31/Ki-67, and GLUT-1 was determined by immunohistochemistry in human perihilar cholangiocarcinomas. In addition, the response of human perihilar cholangiocarcinoma (SK-ChA-1) cells to PDT with liposome-delivered zinc phthalocyanine was investigated under both normoxic and hypoxic conditions. Acriflavine, a HIF-1α/HIF-1β dimerization inhibitor and a potential dual topoisomerase I/II inhibitor, was evaluated for its adjuvant effect on PDT efficacy.

CONCLUSIONS

HIF-1, which is activated in human hilar cholangiocarcinomas, contributes to tumor cell survival following PDT in vitro. Combining PDT with acriflavine pretreatment improves PDT efficacy in cultured cells and therefore warrants further preclinical validation for therapy-recalcitrant perihilar cholangiocarcinomas.

Polymeric Nanoparticles for Cancer Photodynamic Therapy

In chemotherapy a fine balance between therapeutic and toxic effects needs to be found for each patient, adapting standard combination protocols each time. Nanotherapeutics has been introduced into clinical practice for treating tumors with the aim of improving the therapeutic outcome of conventional therapies and of alleviating their toxicity and overcoming multidrug resistance. Photodynamic therapy (PDT) is a clinically approved, minimally invasive procedure emerging in cancer treatment. It involves the administration of a photosensitizer (PS) which, under light irradiation and in the presence of molecular oxygen, produces cytotoxic species. Unfortunately, most PSs lack specificity for tumor cells and are poorly soluble in aqueous media, where they can form aggregates with low photoactivity. Nanotechnological approaches in PDT (nanoPDT) can offer a valid option to deliver PSs in the body and to solve at least some of these issues. Currently, polymeric nanoparticles (NPs) are emerging as nanoPDT system because their features (size, surface properties, and release rate) can be readily manipulated by selecting appropriate materials in a vast range of possible candidates commercially available and by synthesizing novel tailor-made materials. Delivery of PSs through NPs offers a great opportunity to overcome PDT drawbacks based on the concept that a nanocarrier can drive therapeutic concentrations of PS to the tumor cells without generating any harmful effect in non-target tissues. Furthermore, carriers for nanoPDT can surmount solubility issues and the tendency of PS to aggregate, which can severely affect photophysical, chemical, and biological properties. Finally, multimodal NPs carrying different drugs/bioactive species with complementary mechanisms of cancer cell killing and incorporating an imaging agent can be developed. In the following, we describe the principles of PDT use in cancer and the pillars of rational design of nanoPDT carriers dictated by tumor and PS features. Then we illustrate the main nanoPDT systems demonstrating potential in preclinical models together with emerging concepts for their advanced design.

Tumor cell survival pathways activated by photodynamic therapy: a molecular basis for pharmacological inhibition strategies

Photodynamic therapy (PDT) has emerged as a promising alternative to conventional cancer therapies such as surgery, chemotherapy, and radiotherapy. PDT comprises the administration of a photosensitizer, its accumulation in tumor tissue, and subsequent irradiation of the photosensitizer-loaded tumor, leading to the localized photoproduction of reactive oxygen species (ROS). The resulting oxidative damage ultimately culminates in tumor cell death, vascular shutdown, induction of an antitumor immune response, and the consequent destruction of the tumor. However, the ROS produced by PDT also triggers a stress response that, as part of a cell survival mechanism, helps cancer cells to cope with the PDT-induced oxidative stress and cell damage. These survival pathways are mediated by the transcription factors activator protein 1 (AP-1), nuclear factor E2-related factor 2 (NRF2), hypoxia-inducible factor 1 (HIF-1), nuclear factor κB (NF-κB), and those that mediate the proteotoxic stress response. The survival pathways are believed to render some types of cancer recalcitrant to PDT and alter the tumor microenvironment in favor of tumor survival. In this review, the molecular mechanisms are elucidated that occur post-PDT to mediate cancer cell survival, on the basis of which pharmacological interventions are proposed. Specifically, pharmaceutical inhibitors of the molecular regulators of each survival pathway are addressed. The ultimate aim is to facilitate the development of adjuvant intervention strategies to improve PDT efficacy in recalcitrant solid tumors.

Nanoparticle Delivered VEGF-A siRNA Enhances Photodynamic Therapy for Head and Neck Cancer Treatment

Photodynamic therapy (PDT) is believed to promote hypoxic conditions to tumor cells leading to overexpression of angiogenic markers such as vascular endothelial growth factor (VEGF). In this study, PDT was combined with lipid-calcium-phosphate nanoparticles (LCP NPs) to deliver VEGF-A small interfering RNA (siVEGF-A) to human head and neck squamous cell carcinoma (HNSCC) xenograft models. VEGF-A were significantly decreased for groups treated with siVEGF-A in human oral squamous cancer cell (HOSCC), SCC4 and SAS models. Cleaved caspase-3 and in situ TdT-mediated dUTP nick-end labeling assay showed more apoptotic cells and reduced Ki-67 expression for treated groups compared to phosphate buffered saline (PBS) group. Indeed, the combined therapy showed significant tumor volume decrease to ~70 and ~120% in SCC4 and SAS models as compared with untreated PBS group, respectively. In vivo toxicity study suggests no toxicity of such LCP NP delivered siVEGF-A. In summary, results suggest that PDT combined with targeted VEGF-A gene therapy could be a potential therapeutic modality to achieve enhanced therapeutic outcome for HNSCC.

Hypoxia Induced by Upconversion-Based Photodynamic Therapy: Towards Highly Effective Synergistic Bioreductive Therapy in Tumors

Local hypoxia in tumors is an undesirable consequence of photodynamic therapy (PDT), which will lead to greatly reduced effectiveness of this therapy. Bioreductive pro-drugs that can be activated at low-oxygen conditions will be highly cytotoxic under hypoxia in tumors. Based on this principle, double silica-shelled upconversion nanoparticles (UCNPs) nanostructure capable of co-delivering photosensitizer (PS) molecules and a bioreductive pro-drug (tirapazamine, TPZ) were designed (TPZ-UC/PS), with which a synergetic tumor therapeutic effect has been achieved first by UC-based (UC-) PDT under normal oxygen environment, immediately followed by the induced cytotoxicity of activated TPZ when oxygen is depleted by UC-PDT. Treatment with TPZ-UC/PS plus NIR laser resulted in a remarkably suppressed tumor growth as compared to UC-PDT alone, implying that the delivered TPZ has a profound effect on treatment outcomes for the much-enhanced cytotoxicity of TPZ under PDT-induced hypoxia.

MicroRNAs associated with the efficacy of photodynamic therapy in biliary tract cancer cell lines

Photodynamic therapy (PDT) is a palliative treatment option for unresectable hilar biliary tract cancer (BTC) showing a considerable benefit for survival and quality of life with few side effects. Currently, factors determining the cellular response of BTC cells towards PDT are unknown. Due to their multifaceted nature, microRNAs (miRs) are a promising analyte to investigate the cellular mechanisms following PDT. For two photosensitizers, Photofrin® and Foscan®, the phototoxicity was investigated in eight BTC cell lines. Each cell line (untreated) was profiled for expression of n=754 miRs using TaqMan® Array Human MicroRNA Cards. Statistical analysis and bioinformatic tools were used to identify miRs associated with PDT efficiency and their putative targets, respectively. Twenty miRs correlated significantly with either high or low PDT efficiency. PDT was particularly effective in cells with high levels of clustered miRs 25-93*-106b and (in case of miR-106b) a phenotype characterized by high expression of the mesenchymal marker vimentin and high proliferation (cyclinD1 and Ki67 expression). Insensitivity towards PDT was associated with high miR-200 family expression and (for miR-cluster 200a/b-429) expression of differentiation markers Ck19 and Ck8/18. Predicted and validated downstream targets indicate plausible involvement of miRs 20a*, 25, 93*, 130a, 141, 200a, 200c and 203 in response mechanisms to PDT, suggesting that targeting these miRs could improve susceptibility to PDT in insensitive cell lines. Taken together, the miRNome pattern may provide a novel tool for predicting the efficiency of PDT and-following appropriate functional verification-may subsequently allow for optimization of the PDT protocol.

Tumor cells upregulate normoxic HIF-1α in response to doxorubicin

Hypoxia-inducible factor 1 (HIF-1) is a master transcription factor that controls cellular homeostasis. Although its activation benefits normal tissue, HIF-1 activation in tumors is a major risk factor for angiogenesis, therapeutic resistance, and poor prognosis. HIF-1 activity is usually suppressed under normoxic conditions because of rapid oxygen-dependent degradation of HIF-1α. Here, we show that, under normoxic conditions, HIF-1α is upregulated in tumor cells in response to doxorubicin, a chemotherapeutic agent used to treat many cancers. In addition, doxorubicin enhanced VEGF secretion by normoxic tumor cells and stimulated tumor angiogenesis. Doxorubicin-induced accumulation of HIF-1α in normoxic cells was caused by increased expression and activation of STAT1, the activation of which stimulated expression of iNOS and its synthesis of nitric oxide (NO) in tumor cells. Mechanistic investigations established that blocking NO synthesis or STAT1 activation was sufficient to attenuate the HIF-1α accumulation induced by doxorubicin in normoxic cancer cells. To our knowledge, this is the first report that a chemotherapeutic drug can induce HIF-1α accumulation in normoxic cells, an efficacy-limiting activity. Our results argue that HIF-1α-targeting strategies may enhance doxorubicin efficacy. More generally, they suggest a broader perspective on the design of combination chemotherapy approaches with immediate clinical impact.

Upregulation of genes for C-reactive protein and related pentraxin/complement proteins in photodynamic therapy-treated human tumor cells: enrolment of PI3K/Akt and AP-1

Treatment of mouse tumors by photodynamic therapy (PDT) was reported to trigger the production of serum amyloid P component (SAP), a prototypic acute phase reactant in the mouse, that occurs in the targeted tumor as well as distant sites dominated by host's liver. It was also shown that the SAP gene becomes upregulated and protein produced in mouse tumor cells treated by PDT in vitro. Present study revealed that, in addition to SAP, increased expression of genes encoding related pentraxin and complement proteins, including PTX3, C1q and ficolin B, can be found in mouse LLC tumor cells treated by PDT. Since in humans C-reactive protein (CRP) is more important acute phase reactant than SAP, the expression of gene encoding this pentraxin protein was examined in human lung tumor A549 cells treated by PDT. The results demonstrated a PDT dose-dependent upregulation of CRP gene, as well as of PTX3 and ficolin 1 genes in these cells. Investigation into the signal transduction process underlying PDT-induced human CRP gene upregulation using specific inhibitors of critical signaling elements revealed critical role played by PI3K/Akt pathway. Downstream DNA transcription factor largely responsible for this increased CRP gene expression is AP-1 with possible cooperation of HIF-1. It was suggested that cells sensing to have sustained a mortal injury from PDT can turn on molecular programs ensuring that the disposal of their corpses (facilitated by CRP and related pentraxin and complement components) is swift and efficient.

Ecological photodynamic therapy: new trend to disrupt the intricate networks within tumor ecosystem

As with natural ecosystems, species within the tumor microenvironment are connected by pairwise interactions (e.g. mutualism, predation) leading to a strong interdependence of different populations on each other. In this review we have identified the ecological roles played by each non-neoplastic population (macrophages, endothelial cells, fibroblasts) and other abiotic components (oxygen, extracellular matrix) directly involved with neoplastic development. A way to alter an ecosystem is to affect other species within the environment that are supporting the growth and survival of the species of interest, here the tumor cells; thus, some features of ecological systems could be exploited for cancer therapy. We propose a well-known antitumor therapy called photodynamic therapy (PDT) as a novel modulator of ecological interactions. We refer to this as "ecological photodynamic therapy." The main goal of this new strategy is the improvement of therapeutic efficiency through the disruption of ecological networks with the aim of destroying the tumor ecosystem. It is therefore necessary to identify those interactions from which tumor cells get benefit and those by which it is impaired, and then design multitargeted combined photodynamic regimes in order to orchestrate non-neoplastic populations against their neoplastic counterpart. Thus, conceiving the tumor as an ecological system opens avenues for novel approaches on treatment strategies.

Photodynamic therapy-induced angiogenic signaling: consequences and solutions to improve therapeutic response

Photodynamic therapy (PDT) can be a highly effective treatment for diseases ranging from actinic keratosis to cancer. While use of this therapy shows great promise in preclinical and clinical studies, understanding the molecular consequences of PDT is critical to designing better treatment protocols. A number of publications have documented alteration in angiogenic factors and growth factor receptors following PDT, which could abrogate treatment effect by inducing angiogenesis and re-establishment of the tumor vasculature. In response to these findings, work over the past decade has examined the efficacy of combining PDT with molecular targeting drugs, such as anti-angiogenic compounds, in an effort to combat these PDT-induced molecular changes. These combinatorial approaches increase rates of apoptosis, impair pro-tumorigenic signaling, and enhance tumor response. This report will examine the current understanding of PDT-induced angiogenic signaling and address molecular-based approaches to abrogate this signaling or its consequences thereby enhancing PDT efficacy.

Photodynamic therapy augments the efficacy of oncolytic vaccinia virus against primary and metastatic tumours in mice

Background:

Therapies targeted towards the tumour vasculature can be exploited for the purpose of improving the systemic delivery of oncolytic viruses to tumours. Photodynamic therapy (PDT) is a clinically approved treatment for cancer that is known to induce potent effects on tumour vasculature. In this study, we examined the activity of PDT in combination with oncolytic vaccinia virus (OVV) against primary and metastatic tumours in mice.

Methods:

The effect of 2-[1-hexyloxyethyl-]-2-devinyl pyropheophorbide-a (HPPH)-sensitised-PDT on the efficacy of oncolytic virotherapy was investigated against subcutaneously implanted syngeneic murine NXS2 neuroblastoma and human FaDu head and neck squamous cell carcinoma xenografts in nude mice. Treatment efficacy was evaluated by monitoring tumour growth and survival. The effects of combination treatment on vascular function were examined using magnetic resonance imaging (MRI) and immunohistochemistry, whereas viral replication in tumour cells was analysed by a standard plaque assay. Normal tissue phototoxicity following PDT-OV treatment was studied using the mouse foot response assay.

Results:

Combination of PDT with OVV resulted in inhibition of primary and metastatic tumour growth compared with either monotherapy. PDT-induced vascular disruption resulted in higher intratumoural viral titres compared with the untreated tumours. Five days after delivery of OVV, there was a loss of blood flow to the interior of tumour that was associated with infiltration of neutrophils. Administration of OVV did not result in any additional photodynamic damage to normal mouse foot tissue.

Conclusion:

These results provide evidence into the usefulness of PDT as a means of enhancing intratumoural replication and therapeutic efficacy of OV.

Photodynamic sensitivity of esophageal cancer KYSE-70 cells is attenuated by all-trans retinoic acid-induced differentiation

AIM: To investigate the impact of all-trans retinoic acid (ATRA)-induced cell differentiation on photodynamic sensitivity of human esophageal cancer cell line KYSE-70.

METHODS: Both well and poorly differentiated KYSE-450 cell lines were used in this study. KYSE-70 differentiation was induced with 1 µmol/L ATRA and evidenced by cell morphology and proliferation. Phototoxicity after photodynamic therapy (PDT, 450 nm) was detected by MTT assay. Apoptosis was measured by flow cytometry, and morphology of apoptotic cells was visualized after Hoechst 33342 staining.

RESULTS: Cells after ATRA treatment exhibited increased size, reduced cytoplasmic and nuclear density, and nuclear enlargement. Cell growth was inhibited compared to control cells. After PDT treatment, the survival of well differentiated KYSE-450 cells and ATRA-treated KYSE-70 cells were reduced compared to poorly differentiated KYSE-70 cells. Cell viability differed significantly between ATRA-treated and non-treated KYSE-70 cells after PDT treatment (54.28% ± 3.64% vs 36.23% ± 7.43%, P < 0.001). The percentage of apoptotic cells in ATRA-induced KYSE-70 cells was less than that in non-treated KYSE-70 cells (18.1% vs 33.3%, P < 0.05).

CONCLUSION: ATRA-induced cell differentiation decreases photodynamic sensitivity of esophageal cancer KYSE-70 cells possibly by inducing resistance to apoptosis.

Increasing the efficiency of photodynamic therapy by improved light delivery and oxygen supply using an anticoagulant in a solid tumor model

BACKGROUND AND OBJECTIVE

The main factors in photodynamic therapy (PDT) are: photosensitizer retention, photon absorption, and oxygen supply. Each factor has its unique set of problems that poses limitation to the treatment. Both light delivery and oxygen supply are significant bottlenecks in PDT. Vascular closure during PDT reduces oxygen supply to the targeted tissue. On the other hand, with the changes in blood perfusion, the tissue optical properties change, and result in variation in irradiation light transmission. For these reasons, it becomes very important to avoid blood coagulation and vascular closure during PDT.

STUDY DESIGN/MATERIALS AND METHODS

The efficiency of PDT combined with the anticoagulant heparin was studied in a BALB/c mouse model with subcutaneous EMT6 mammary carcinomas. Mice were randomized into three groups: control, PDT-only, and PDT with heparin. The photosensitizer Photofrin was used in our experiments. Light transmission, blood perfusion, and local production of reactive oxygen species (ROS) were monitored during the treatment. The corresponding histological examinations were performed to determine the thrombosis immediately after irradiation and to evaluate tumor necrosis 48 hours after the treatment.

RESULTS

The results clearly demonstrated that PDT combined with pre-administered heparin can significantly reduce thrombosis during light irradiation. The blood perfusion, oxygen supply, and light delivery are all improved. Improved tumor responses in the combined therapy, as shown with the histological examination and tumor growth assay, are clearly demonstrated and related to an increased local ROS production.

CONCLUSION

Transitory anticoagulation treatment significantly enhances the antitumor effect of PDT. It is mainly due to the improvement of the light delivery and oxygen supply in tumor, and ultimately the amount of ROS produced during PDT.

Photodynamic therapy: illuminating the road from cell death towards anti-tumour immunity

Photodynamic therapy (PDT) utilizes the destructive power of reactive oxygen species generated via visible light irradiation of a photosensitive dye accumulated in the cancerous tissue/cells, to bring about their obliteration. PDT activates multiple signalling pathways in cancer cells, which could give rise to all three cell death modalities (at least in vitro). Simultaneously, PDT is capable of eliciting various effects in the tumour microenvironment thereby affecting the tumour-associated/-infiltrating immune cells and by extension, leading to infiltration of various immune cells (e.g. neutrophils) into the treated site. PDT is also associated to the activation of different immune phenomena, e.g. acute-phase response, complement cascade and production of cytokines/chemokines. It has also come to light that, PDT is capable of activating 'anti-tumour adaptive immunity' in both pre-clinical as well as clinical settings. Although the ability of PDT to induce 'anti-cancer vaccine effect' is still debatable, yet it has been shown to be capable of inducing exposure/release of certain damage-associated molecular patterns (DAMPs) like HSP70. Therefore, it seems that PDT is unique among other approved therapeutic procedures in generating a microenvironment suitable for development of systemic anti-tumour immunity. Apart from this, recent times have seen the emergence of certain promising modalities based on PDT like-photoimmunotherapy and PDT-based cancer vaccines. This review mainly discusses the effects exerted by PDT on cancer cells, immune cells as well as tumour microenvironment in terms of anti-tumour immunity. The ability of PDT to expose/release DAMPs and the future perspectives of this paradigm have also been discussed.

Calculation of cellular oxygen concentration for photodynamic therapy in vitro

In vitro photodynamic therapy experiments are usually performed by irradiating cells in confluent or nearly confluent monolayer cultures. Oxygen is consumed in the monolayer by photodynamic reactions and cellular respiration and is supplied by diffusion from the overlying medium. Calculations of oxygen concentration by numerical solution of the time-dependent diffusion equation show that hypoxia can be induced in the monolayer under typical PDT conditions and that this will limit the total treatment effect. There is an optimum fluence rate at which the greatest singlet oxygen dose can be delivered before hypoxia becomes limiting. It is recommended that researchers use these calculations to avoid hypoxia or confirm that fortuitous oxygen transport by other mechanisms (e.g., convection) is adequate to prevent it.

Knock down of the dual functional protein apurinic /apyrimidinic endonuclease 1 enhances the killing effect of hematoporphrphyrin derivative-mediated photodynamic therapy on non-small cell lung cancer cells in vitro and in a xenograft model

Photodynamic therapy (PDT) is considered to be effective treatment for many cancers including lung cancer, head and neck cancers, and prostate cancer. It uses the combination of nontoxic photosensitizers and harmless visible light to generate reactive oxygen species and kill cells. However, DNA repair and reactive oxygen species-induced signaling pathway activation play crucial roles in cellular response to PDT and may also result in therapeutic limitation of PDT. To improve the cancer therapeutic efficacy of PDT, we targeted apurinic/apyrimidinic endonuclease (APE1), which is essential for both DNA repair and redox regulation of gene transcription, as a potential candidate for PDT combined gene therapy. In our study, an adenovirus-mediated APE1 silencing strategy was introduced to test its therapeutic enhancement for the non-small cell lung cancer cell line A549 both in vitro and in vivo after hematoporphrphyrin derivative (HpD)-mediated PDT. The adenovirus vector Ad5/F35-shAPE1 was validated to significantly suppress the protein expression of APE1 in cultured A549 cell and in its xenograft of nude mice. Ad5/F35-shAPE1 effectively inhibited APE1 protein upregulation induced by PDT and resulted in an increase in A549 cell killing by photoirradiation compared with the hematoporphrphyrin derivative-PDT alone group. Ad5/F35-shAPE1 suppressed the DNA repair capacity for single-strand breaks and abolished the activation of some stress-related transcription factors such as hypoxia-induced factor (HIF)-1 that consequently lead to increased cell apoptosis after PDT. Additionally, knock down of APE1 enhanced the tumor suppression efficacy of PDT on the A549 xenograft. Our study indicated that APE1-targeted gene therapy combined with PDT is a promising strategy for enhancement of the efficacy of PDT in treatment of non-small cell lung cancer.

Sensitization of cerebral tissue in nude mice with photodynamic therapy induces ADAM17/TACE and promotes glioma cell invasion

In the present study, we tested the hypothesis that a mild cerebral tissue injury promotes subsequent glioma invasion via activation of the ADAM17-EGFR-PI3K-Akt pathway. Mild injury was induced by photodynamic therapy (PDT), which employs tissue-penetrating laser light exposure following systemic administration of a tumor-localizing photosensitizer. Athymic nude mice were treated with sublethal PDT (80 J/cm2 with 2 mg/kg Photofrin). Hypoxic stress and ADAM17-EGFR-PI3K-Akt were measured using Western blot and immunostaining. Additional groups with/without pro-sublethal PDT were subsequently implanted with U87 glioma tumor cell. Tumor invasion and ADAM17-EGFR-PI3K-Akt pathway in tumor area were measured. After a sublethal dose of PDT, HIF-1alpha expression was increased by a factor of three in PDT-treated normal brain tissue compared to contralateral control brain tissue. PDT-treated brain tissue exhibited a significant increase in ADAM17, p-EGFR, p-Akt expression compared to non-treated tissue. ADAM17 positive area significantly increased from 1.78% to 10.89%. The percentage of p-EGFR and p-Akt positive cells significantly increased from 9.50% and 14.50% to 21.31% and 32.29%, respectively, PDT treatment significantly increased subsequent implanted U87 glioma cell invasion by 3.68-fold and increased ADAM17, EGFR, p-EGFR, Akt, p-Akt expression by 178%, 43.9%, 152.7%, 89.6%,and 164.2%, respectively, compared to control group. Our data showed that a sublethal sensitization of cerebral tissue with PDT significantly increased U87 cell invasion in nude mice, and that glioma cell invasion is highly correlated with activation of the ADAM17-EGFR-PI3K-Akt pathway (r=0.928, 0.775, 0.870, 0.872, and 0.883, respectively), most likely via HIF-1alpha.

Photodynamic therapy in the treatment of actinic keratosis

The efficacy of photodynamic therapy (PDT) with 5-aminolevulinate and methyl aminolevulinate in the treatment of actinic keratosis has been demonstrated in a large number of clinical studies over the last several years. Here, we recapitulate the major findings, comparing the various photosensitizers, light sources and therapeutic regimens, and present a retrospective analysis of 142 own cases treated with 259 PDTs. In addition, we also discuss the value of PDT in comparison with cryotherapy or 5-fluorouracil. The efficacy and the low risk of side effects of PDT have resulted in a high patient preference in clinical trials.

Multiple Components of Photodynamic Therapy Can Phosphorylate Akt?

A growing number of clinically relevant molecular and cellular responses are observed following photodynamic therapy (PDT). PDT-mediated oxidative stress and PDT-induced tissue hypoxia can elicit the transcriptional and/or translational expression of genes associated with cellular stress, inflammation, angiogenesis, immuno-modulation, apoptosis and signal transduction. One of the signaling molecules activated by oxidative stress is Akt/protein kinase B. Phosphorylation of Akt/protein kinase B activates this signaling molecule and induces a survival response in effected cells and tissue. We hypothesized that PDT using Photofrin (PH) as the photosensitizer could also induce increased levels of Akt phosphorylation. Results from our initial set of experiments demonstrated that in vitro and in vivo PDT treatments induced Akt phosphorylation. Interestingly, incubation of mouse and human breast cancer cells with the porphyrin-based photosensitizer, PH, increased the expression of Akt phosphorylation in the absence of light. Exposure of the corresponding mouse and human-derived breast cancer tumors growing in mice to 630 nm light in the absence of PH administration also induced Akt phosphorylation. These results demonstrate that individual components of the PDT process, photosensitizer alone and light alone, as well as the complete PDT procedure can activate the Akt signaling pathway.

Analyzing effects of photodynamic therapy with 5-aminolevulinic acid (ALA) induced protoporphyrin IX (PPIX) in urothelial cells using reverse phase protein arrays

Photodynamic therapy (PDT) using 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PPIX) is clinically established approach for a number of defined applications. However, in order to optimize the therapeutic benefits of PDT, the specific mode of cell destruction should be better defined. Apoptosis is favored over necrosis for clinical practice as the latter causes more side-effects. In the present study, we analyse PDT-induced cell death and its correlation to various PDT parameters (different doses applied, time after PDT treatment) in vitro using reverse phase protein arrays. Human urothelial cell lines with varying degrees of differentiation (UROtsa, RT4, RT112, J82) were subjected to in vitro-PDT using increasing doses of irradiation. In addition, positive controls for apoptosis, necrosis and un-/specific cellular damage were included. Cells were harvested over a specified time course, lysed and arrayed onto nitrocellulose-covered glass slides. The arrays were analyzed for expression of apoptosis-related proteins by immunohistochemistry. Analysis of caspase-3 and -9 expression, the activation of HIF-1alpha, Bcl2, Cox2 and the phosphorylation of AKT reveals signal activation due to a PDT-stimulus in correlation with the positive controls. Data were analyzed by unsupervised hierarchical clustering and depicted as a heat map revealing cell-specific patterns of pathway stimulation. Higher differentiated phenotypes showed a more distinct signal response in general and a higher apoptotic response in detail. Lower differentiated cell lines lost pathway regulation capabilities according to their state of dedifferentiation. Reverse phase protein arrays are a promising technique for signal pathway profiling: they exceed the range of traditional western blots by sensitivity, high-throughput capability, minimal sample consumption and easy quantification of results obtained.